5 - Development of Heart, Kidneys and Lungs Flashcards
What embryonic tissue gives rise to the heart
The lateral plate mesoderm, specifically the heart field
Mesodermal origin
Arises from the lateral plate mesoderm, specifically the heart field
Which molecules control specification of heart precursor cells
BMP4 (promotes heart field), and Noggin (promotes somite formation); they inhibit each other
How does Wnt signalling affect heart development
Wnt from the neural tube inhibits heart formation, while Wnt antagonists from the anterior endoderm promote it
What role does Fibronectin play in heart development
Guides heart precursor migration; it’s expressed in an anterior-posterior gradient in the endoderm
Which gene is essential for heart precursor formation
Nkx2.5
What evidence supports the importance of Nkx2.5
Drosophila without Nkx2.5 = no heart
Humans with mutations = congenital heart defects
Nkx2.5 mutant mice = embryonic death due to severe heart defects
How is the linear heart tube formed
Heart precursors migrate medially from both sides and fuse, forming a linear heart tube
What happens if heart precursor cells fail to migrate properly
Cardia bifida – the heart precursors don’t fuse, leading to two separate hearts
What regulates heart tube looping and chamber formation
Hox genes and other regional genes define different domains
Left-right asymmetry genes regulate the direction of looping
What condition results from defective heart tube looping
Situs inversus – reversed positioning of internal organs
What embryonic tissue gives rise to the kidneys
Intermediate mesoderm
What signals are involved in specifying the intermediate mesoderm
BMP gradient (from lateral plate mesoderm)
Signals from somites (paraxial mesoderm)
Transcription factors: Pax2 and Pax8
What are the three kidney regions in order of development
Pronephros (degenerates in humans)
Mesonephros (transient, contributes to male reproductive tract)
Metanephros (becomes the adult kidney)
What induces ureteric bud outgrowth
GDNF (from the metanephric mesenchyme) binding to cRet receptors on the nephric duct
What triggers nephron formation
Wnt signals from the ureteric bud induce mesenchymal-to-epithelial transition (MET), forming renal vesicles → nephrons
What gene is essential for kidney development and linked to a childhood cancer
Wt1 – mutations can lead to Wilms’ tumour
What embryonic tissue gives rise to the lungs
The anterior endoderm, specifically the foregut
What is the lung bud and where does it form
The laryngotracheal groove, which emerges ventrally from the foregut
What signals regulate lung bud formation
Retinoic Acid (RA) from mesoderm
Wnt signalling
Loss of either results in no lung formation
What structures arise from lung bud branching
Bronchial buds
Left vs Right lung buds
Left lung → 2 primary bronchi
Right lung → 3 primary bronchi
How does the surrounding mesoderm affect lung branching
Tracheal mesenchyme inhibits branching
Bronchial mesenchyme promotes branching
What experimental evidence supports the mesenchymal influence on lung branching
Placing tracheal mesenchyme on bronchial tip → less branching
Placing bronchial mesenchyme on tracheal tip → more branching
